19G 
GEOLOGY OF THE FOURTH DISTRICT. 
retiring sea has left above its reach, so much do these soft shales resemble the mud deposits 
on the bays and creeks along the sea shore. 
The following woodcuts are illustrations of the prevailing forms in different parts of the 
group. Those from the lowest portions are omitted. 
78. 
]. Bellerophon patulua. 
2. Microdon bellastriata. 
3. Cucullea opium. 
4. Nucula oblonga. 7. Nucula bellatula. 
5. Nucula lineata. 8. Cypricardia truncata. 
6. Tellina? ovata. 9. Modiola concentrica. 
1 . Bellerophon patulus, n. s. — Sides slightly umbilicated, aperture suddenly and broadly 
dilated, nearly smooth, or with faint undulating striae, which become stronger and slightly 
arched in receding from the margin. 
The striae become very strong and sharply arched upon the first volution. 
Locality — Cayuga lake shore. 
2. Microdon bellastriata (Conrad, Jour. Acad. Nat. Sci. Vol. 8, p. 247, pi. 13, fig. 12).— 
Compressed, broadly oval and somewhat truncated posteriorly; marked by numerous equal 
concentric striae. 
This is a beautiful and easily recognized shell. It is often abundant in the harder shales, 
but in the western part of the district is exceedingly rare. It is one of those fossils having a 
wide geographical range, being known in the middle and southwestern parts of Virginia. 
The young of this shell closely resembles the figure of Venus parallela (Phil. Geol. 
Yorkshire, Part ii, pi. 5, fig. 8). 
Locality — Banks of Seneca and Cayuga lake ; Crooked lake outlet; more rarely in the 
Genesee valley. 
